This tutorial shows how to set up a high-availability storage with two storage servers (CentOS 5.4) that use GlusterFS. Each storage server will be a mirror of the other storage server, and files will be replicated automatically across both storage servers. The client system (CentOS 5.4 as well) will be able to access the storage as if it was a local filesystem. GlusterFS is a clustered file-system capable of scaling to several peta-bytes. It aggregates various storage bricks over Infiniband RDMA or TCP/IP interconnect into one large parallel network file system. Storage bricks can be made of any commodity hardware such as x86_64 servers with SATA-II RAID and Infiniband HBA.
I do not issue any guarantee that this will work for you!
1 Preliminary Note
In this tutorial I use three systems, two servers and a client:
- server1.example.com: IP address 192.168.0.100 (server)
- server2.example.com: IP address 192.168.0.101 (server)
- client1.example.com: IP address 192.168.0.102 (client)
All three systems should be able to resolve the other systems’ hostnames. If this cannot be done through DNS, you should edit the /etc/hosts file so that it contains the following lines on all three systems:
vi /etc/hosts
[...] 192.168.0.100 server1.example.com server1 192.168.0.101 server2.example.com server2 192.168.0.102 client1.example.com client1 [...] |
(It is also possible to use IP addresses instead of hostnames in the following setup. If you prefer to use IP addresses, you don’t have to care about whether the hostnames can be resolved or not.)
2 Setting Up The GlusterFS Servers
server1.example.com/server2.example.com:
GlusterFS isn’t available as a package for CentOS 5.4, therefore we have to build it ourselves. First we install the prerequisites:
yum groupinstall ‘Development Tools’
yum groupinstall ‘Development Libraries’
yum install libibverbs-devel fuse-devel
Then we download the latest GlusterFS release from http://www.gluster.org/download.php and build it as follows:
cd /tmp
wget http://ftp.gluster.com/pub/gluster/glusterfs/2.0/LATEST/glusterfs-2.0.9.tar.gz
tar xvfz glusterfs-2.0.9.tar.gz
cd glusterfs-2.0.9
./configure
At the end of the ./configure command, you should see something like this:
[...]
GlusterFS configure summary
===========================
FUSE client : yes
Infiniband verbs : yes
epoll IO multiplex : yes
Berkeley-DB : yes
libglusterfsclient : yes
argp-standalone : no
[root@server1 glusterfs-2.0.9]#
make && make install
ldconfig
Check the GlusterFS version afterwards (should be 2.0.9):
glusterfs –version
[root@server1 glusterfs-2.0.9]# glusterfs –version
glusterfs 2.0.9 built on Mar 1 2010 15:34:50
Repository revision: v2.0.9
Copyright (c) 2006-2009 Gluster Inc. <http://www.gluster.com>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GlusterFS under the terms of the GNU General Public License.
[root@server1 glusterfs-2.0.9]#
Next we create a few directories:
mkdir /data/
mkdir /data/export
mkdir /data/export-ns
mkdir /etc/glusterfs
Now we create the GlusterFS server configuration file /etc/glusterfs/glusterfsd.vol which defines which directory will be exported (/data/export) and what client is allowed to connect (192.168.0.102 = client1.example.com):
vi /etc/glusterfs/glusterfsd.vol
volume posix type storage/posix option directory /data/export end-volume volume locks type features/locks subvolumes posix end-volume volume brick type performance/io-threads option thread-count 8 subvolumes locks end-volume volume server type protocol/server option transport-type tcp option auth.addr.brick.allow 192.168.0.102 subvolumes brick end-volume |
Please note that it is possible to use wildcards for the IP addresses (like 192.168.*) and that you can specify multiple IP addresses separated by comma (e.g. 192.168.0.102,192.168.0.103).
Afterwards we create the following symlink…
ln -s /usr/local/sbin/glusterfsd /sbin/glusterfsd
… and then the system startup links for the GlusterFS server and start it:
chkconfig –levels 35 glusterfsd on
/etc/init.d/glusterfsd start
3 Setting Up The GlusterFS Client
client1.example.com:
GlusterFS isn’t available as a package for CentOS 5.4, therefore we have to build it ourselves. First we install the prerequisites:
yum groupinstall ‘Development Tools’
yum groupinstall ‘Development Libraries’
yum install libibverbs-devel fuse-devel
Then we load the fuse kernel module…
modprobe fuse
… and create the file /etc/rc.modules with the following contents so that the fuse kernel module will be loaded automatically whenever the system boots:
vi /etc/rc.modules
modprobe fuse |
Make the file executable:
chmod +x /etc/rc.modules
Then we download the GlusterFS 2.0.9 sources (please note that this is the same version that is installed on the server!) and build GlusterFS as follows:
cd /tmp
wget http://ftp.gluster.com/pub/gluster/glusterfs/2.0/LATEST/glusterfs-2.0.9.tar.gz
tar xvfz glusterfs-2.0.9.tar.gz
cd glusterfs-2.0.9
./configure
At the end of the ./configure command, you should see something like this:
[...]
GlusterFS configure summary
===========================
FUSE client : yes
Infiniband verbs : yes
epoll IO multiplex : yes
Berkeley-DB : yes
libglusterfsclient : yes
argp-standalone : no
make && make install
ldconfig
Check the GlusterFS version afterwards (should be 2.0.9):
glusterfs –version
[root@client1 glusterfs-2.0.9]# glusterfs –version
glusterfs 2.0.9 built on Mar 1 2010 15:58:06
Repository revision: v2.0.9
Copyright (c) 2006-2009 Gluster Inc. <http://www.gluster.com>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GlusterFS under the terms of the GNU General Public License.
[root@client1 glusterfs-2.0.9]#
Then we create the following two directories:
mkdir /mnt/glusterfs
mkdir /etc/glusterfs
Next we create the file /etc/glusterfs/glusterfs.vol:
vi /etc/glusterfs/glusterfs.vol
volume remote1 type protocol/client option transport-type tcp option remote-host server1.example.com option remote-subvolume brick end-volume volume remote2 type protocol/client option transport-type tcp option remote-host server2.example.com option remote-subvolume brick end-volume volume replicate type cluster/replicate subvolumes remote1 remote2 end-volume volume writebehind type performance/write-behind option window-size 1MB subvolumes replicate end-volume volume cache type performance/io-cache option cache-size 512MB subvolumes writebehind end-volume |
Make sure you use the correct server hostnames or IP addresses in the option remote-host lines!
That’s it! Now we can mount the GlusterFS filesystem to /mnt/glusterfs with one of the following two commands:
glusterfs -f /etc/glusterfs/glusterfs.vol /mnt/glusterfs
or
mount -t glusterfs /etc/glusterfs/glusterfs.vol /mnt/glusterfs
You should now see the new share in the outputs of…
mount
[root@client1 ~]# mount
/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
glusterfs#/etc/glusterfs/glusterfs.vol on /mnt/glusterfs type fuse (rw,allow_other,default_permissions,max_read=131072)
[root@client1 ~]#
… and…
df -h
[root@client1 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
29G 2.2G 25G 9% /
/dev/sda1 99M 13M 82M 14% /boot
tmpfs 187M 0 187M 0% /dev/shm
glusterfs#/etc/glusterfs/glusterfs.vol
28G 2.3G 25G 9% /mnt/glusterfs
[root@client1 ~]#
(server1.example.com and server2.example.com each have 28GB of space for the GlusterFS filesystem, but because the data is mirrored, the client doesn’t see 56GB (2 x 28GB), but only 28GB.)
Instead of mounting the GlusterFS share manually on the client, you could modify /etc/fstab so that the share gets mounted automatically when the client boots.
Open /etc/fstab and append the following line:
vi /etc/fstab
[...] /etc/glusterfs/glusterfs.vol /mnt/glusterfs glusterfs defaults 0 0 |
To test if your modified /etc/fstab is working, reboot the client:
reboot
After the reboot, you should find the share in the outputs of…
df -h
… and…
mount
4 Testing
Now let’s create some test files on the GlusterFS share:
client1.example.com:
touch /mnt/glusterfs/test1
touch /mnt/glusterfs/test2
Now let’s check the /data/export directory on server1.example.com and server2.example.com. The test1 and test2 files should be present on each node:
server1.example.com/server2.example.com:
ls -l /data/export
[root@server1 ~]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2010-02-22 16:50 test1
-rw-r–r– 1 root root 0 2010-02-22 16:50 test2
[root@server1 ~]#
Now we shut down server1.example.com and add/delete some files on the GlusterFS share on client1.example.com.
server1.example.com:
shutdown -h now
client1.example.com:
touch /mnt/glusterfs/test3
touch /mnt/glusterfs/test4
rm -f /mnt/glusterfs/test2
The changes should be visible in the /data/export directory on server2.example.com:
server2.example.com:
ls -l /data/export
[root@server2 ~]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2010-02-22 16:50 test1
-rw-r–r– 1 root root 0 2010-02-22 16:53 test3
-rw-r–r– 1 root root 0 2010-02-22 16:53 test4
[root@server2 ~]#
Let’s boot server1.example.com again and take a look at the /data/export directory:
server1.example.com:
ls -l /data/export
[root@server1 ~]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2010-02-22 16:50 test1
-rw-r–r– 1 root root 0 2010-02-22 16:50 test2
[root@server1 ~]#
As you see, server1.example.com hasn’t noticed the changes that happened while it was down. This is easy to fix, all we need to do is invoke a read command on the GlusterFS share on client1.example.com, e.g.:
client1.example.com:
ls -l /mnt/glusterfs/
[root@client1 ~]# ls -l /mnt/glusterfs/
total 0
-rw-r–r– 1 root root 0 2010-02-22 16:50 test1
-rw-r–r– 1 root root 0 2010-02-22 16:53 test3
-rw-r–r– 1 root root 0 2010-02-22 16:53 test4
[root@client1 ~]#
Now take a look at the /data/export directory on server1.example.com again, and you should see that the changes have been replicated to that node:
server1.example.com:
ls -l /data/export
[root@server1 ~]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2010-02-22 16:50 test1
-rw-r–r– 1 root root 0 2010-02-22 16:53 test3
-rw-r–r– 1 root root 0 2010-02-22 16:53 test4
[root@server1 ~]#
5 Links
- GlusterFS: http://www.gluster.org/
- CentOS: http://www.centos.org/